The present invention relates to a two-bladed vertical axis turbine, particularly for wind, although the same principles apply to other fluids. We have found on simulations that such turbines have higher efficiencies than similar ones with different numbers of blades, for both drag and lift configurations, and the present application describes innovative ways to improve their performance and construction. Some of these principles apply to turbines with different numbers of blades. The two-bladed concept can be extended to two sets of two blades on the same level. This is particularly advantageous in combining drag and lift type blades to achieve the advantages of both. Large lift blades take on rpm characteristics of drag type blades; thus one of the innovations of the current application is defining how they can function together.